Laboratory sample tubes, sometimes called microtubes or cryovials, are normally stored in SBS-formatted storage racks. One of the most common sizes is a 96-tube storage rack which includes eight rows and twelve columns of tube receptacles for holding 96 sample tubes. SBS format standards petinent to tube storage racks are ANSI/SLAS 1-2004 (footprint dimensions, e.g., 85.48 mm ×127.76 mm) and ANSI/SLAS 4-2004 (well positions, e.g. 9 mm spacing for 8×12 well array). Storage racks designed to hold larger sample tubes typically hold 48 or 24 tubes. The sample tubes normally have screw caps to seal the top of tubes. A 2-D barcode is often printed on the bottom of the tubes for automated tracking purposes. Most storage racks contain openings in the bottom of the rack to enable a barcode reader to read the 2-D barcodes from below the rack.
Screw caps on sample tubes can be removed manually but this is a tedious process. Therefore, robotic machines have been designed to automatically screw caps on or screw caps off of sample tubes when the tubes are held in a tube storage rack. This kind of robotic machine is known as a capper, a decapper, or a combined capper/decapper. The machines typically include a header with spaced-apart, rotatable fittings designed to engage the head of respective caps in a row of sample tubes in an SBS-formatted storage rack placed in a nest below the header. To remove caps, the header is lowered robotically so that the fittings, or bits on the fittings, engage the heads of the respective cap for a row of tubes. The bits seat within the head of the respective cap and then turn the caps simultaneously by rotating the fittings counterclockwise. After the caps are removed from tubes on a source rack, they are normally placed in an array on another rack that serves as a cache for the caps. After the samples in the open tubes have been used, the caps on the cache rack are then screwed back on to the respective tubes in a similar fashion.
There are several sample tube manufacturers and it is not uncommon for these manufacturers to each have a unique head configuration for the screw cap. Present day laboratories tend to use several labware manufacturers, opting to implement various forms of research with different brands of microtubes or sample tubes, each with specific advantages for a given application. Since there are a wide variety of such configurations, some capper and decapper systems have removable adapter bit sets for the rotating fittings on the header. These adapter bit sets are typically manually removed and replaced with another bit set when it is desired to remove or place caps on a different brand of sample tubes. The process of exchanging adapter bits is also time-consuming.